1. Field of the Invention
The present invention relates to an exerciser for a steam turbine emergency shutoff valve for steam turbines manufactured by Elliott Co., frame sizes AYR, BYR, BYRH, BYRHH, CYR, DYR, and E-Line turbines with standard Elliott trip systems.
2. Background of the Invention
The emergency shutoff valve, or trip valve, is used on the above mentioned steam turbines to shut off the flow of steam, which is the power source for the turbine, in case of an overspeed condition of the turbine or in some cases, when the unit is set up, for a low oil pressure condition. These turbines are used as general purpose power supplies throughout refineries, chemical plants, power plants and other areas where steam is generated for heating.
The goal of long term runs, more than one year, has been desired due to lost production when the turbines are shut down, man power required to go through the procedure of transferring production to another source, and the potential of causing damage to the turbine during shut down and start-up.
The problems that these emergency shutoff valves have are that they will not always operate properly when a situation such as overspeed or low oil pressure requires that the steam flow is shut off. When the turbine is run for more than one year, in some cases less time, there are contaminants from the steam treatments that will collect around the area where a valve stem of the emergency shutoff valve engages the body of the valve. Another area that is a concern is the hinge pin connection of a resetting lever to the valve mechanism. This hinge pin for the emergency shutoff valve is subjected to all weather related problems and in some cases chemical corrosion and over time will seize up due to a lack of movement.
Since the emergency shutoff valve operates during a turbine emergency, the fact that it will not always operate is a major safety concern within the plants that operate them. These units have actually exploded and caused death due to overspeed conditions for various reasons such as improper methods of trying to check this device. The only safe way to check this system currently, is to shut the turbine down and move the components by hand and then start the turbine back up. It is impossible to safely move these parts during operation with the existing design.
To insure proper operation of the components of an emergency shutoff valve, the parts need to be "exercised." An exerciser consists of a number of components that are assembled on the existing emergency shutoff valve and provide a means for an operator to move the problem components in a controlled manner. An exerciser will also allow the operator to shut off the flow of steam to the turbine during exercising of the valve components in case the turbine starts to go into an overspeed condition or any other emergency occurs. There is currently no exerciser known in the art for the Elliott Co. steam turbines listed above.
Therefore, it is evident that presently the emergency shutoff valve cannot predictably and safely be maintained without temporarily removing the turbine from service. Removal of the turbine from service is disruptive and counterproductive for the businesses depending on the turbine to meet energy needs. The present invention provides a means for extending the uninterrupted run times of a turbine through safe and effective exercising of the shutoff valve. Therefore, the present invention will significantly increase the uninterrupted run times of the subject turbines.
Steam turbine valves have much higher corrosion potential because of the environment surrounding the component materials. Operators of steam turbines are likely to have more confidence in corrosive-resistant material components than those materials that are more conducive to corrosion. Serviceability of the turbine valves is much easier when corrosion is not present, or is reduced. Accordingly, components such as an emergency shutoff valve exerciser are affected less by corrosion if composed of corrosive-resistant materials.